1. Field of the Invention
This invention generally relates to acoustic transmitters and receivers and, more particularly, to systems for generating the images of objects by using acoustic waves.
2. Description of the Prior Art
While the present invention is generally directed to the same field as U.S. Pat. No. 3,875,550 issued on Apr. 1, 1975 and entitled "Electronically Focused Imaging System and Method," the present invention is principally directed to improvements of the inventions therein described and claimed, as will more particularly appear hereinafter. The above identified letters patent bears U.S. Ser. No. 379,760 and was filed on July 16, 1973, by the present inventors and is assigned to the present assignee.
Heretofore acoustic imaging systems have required N.sup.2 locations or spots on the object of interest, N being any positive real integer. Although these arrays provide good focusing and image resolution, there is a practical limit on the maximum size of such an array. When arrays having 100 by 100 elements are constructed, the large number of transducers, terminal connections, amplifiers, and other circuit elements required makes the system unduly complex and very cumbersome.
In the above identified letters patent the array of transducers is electrically scanned at the same speed in both the vertical and horizontal directions. Two delay lines are used for each array and a raster, inclined at 45.degree., is developed by varying the time delay between the horizontal and vertical scans. Since the raster is inclined at 45.degree., the output from the system can be displayed on an oscilloscope but cannot be readily used for a direct television display without the use of a scan converter. In addition, a 45.degree. raster does not efficiently utilize the corner transducer elements located opposite the major scan diagonal.